Circadian pacemaker coupling by multi-peptidergic neurons in the cockroach <Emphasis Type="Italic">Leucophaea maderae</Emphasis> |
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Authors: | Sandra Soehler Monika Stengl Thomas Reischig |
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Institution: | 1.Department of Natural Sciences, Animal Physiology,University of Kassel,Kassel,Germany;2.Department of Neurobiology, Johann Friedrich Blumenbach Institute of Zoology and Anthropology,Georg August University of G?ttingen,G?ttingen,Germany |
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Abstract: | Lesion and transplantation studies in the cockroach, Leucophaea maderae, have located its bilaterally symmetric circadian pacemakers necessary for driving circadian locomotor activity rhythms to
the accessory medulla of the optic lobes. The accessory medulla comprises a network of peptidergic neurons, including pigment-dispersing
factor (PDF)-expressing presumptive circadian pacemaker cells. At least three of the PDF-expressing neurons directly connect
the two accessory medullae, apparently as a circadian coupling pathway. Here, the PDF-expressing circadian coupling pathways
were examined for peptide colocalization by tracer experiments and double-label immunohistochemistry with antisera against
PDF, FMRFamide, and Asn13-orcokinin. A fourth group of contralaterally projecting medulla neurons was identified, additional to the three known groups.
Group one of the contralaterally projecting medulla neurons contained up to four PDF-expressing cells. Of these, three medium-sized
PDF-immunoreactive neurons coexpressed FMRFamide and Asn13-orcokinin immunoreactivity. However, the contralaterally projecting largest PDF neuron showed no further peptide colocalization,
as was also the case for the other large PDF-expressing medulla cells, allowing the easy identification of this cell group.
Although two-thirds of all PDF-expressing medulla neurons coexpressed FMRFamide and orcokinin immunoreactivity in their somata,
colocalization of PDF and FMRFamide immunoreactivity was observed in only a few termination sites. Colocalization of PDF and
orcokinin immunoreactivity was never observed in any of the terminals or optic commissures. We suggest that circadian pacemaker
cells employ axonal peptide sorting to phase-control physiological processes at specific times of the day. |
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